(1) Field of the Invention
The present invention relates to methods of packaging integrated circuit devices, and more particularly, to methods of packaging integrated circuit devices without die corner delamination.
(2) Description of the Prior Art
In the assembly of integrated circuit devices, super ball grid array (SBGA) techniques have become widely used to electrically attach component packages and to mount them on interconnection substrates such as interposer or printed circuit boards. For example, FIG. 1A shows in top view and FIG. 1B shows a cross-sectional view of a SBGA substrate 10. An integrated circuit chip 12 has been mounted on the SBGA substrate. Now, the chip 12 is to be encapsulated with a liquid resin, for example, to protect the chip. This is especially important for low dielectric constant material wafers since they are very expensive. For example, a low-k wafer has a dielectric material more brittle than fluorinated silicate glass (FSG).
A high viscosity material is applied as a dam 14. Then an encapsulation material is dispensed within the area surrounded by the dam, as shown by 16 in FIGS. 2A and 2B. The encapsulation material has a lower viscosity than the dam material. However, thermal cycling testing shows that the liquid encapsulation material 16 suffers delamination at the die corner due to shrinking of the encapsulation layer. High global stress is found at the die corner. This is caused by the mismatch between the coefficient of thermal expansion of the die and the encapsulation material.
FIG. 3 shows an enlarged view of the die 12 showing shrinking 22 of the encapsulation material 16 during curing. Layer 18 represents the active metal circuit layers. The encapsulation material peels up from the surface of the substrate as shown in 20. It is desired to find a way to prevent delamination at the die corner in order to enhance the reliability and yield of SBGA assembly.
U.S. Pat. No. 6,127,724 to DiStefano and U.S. Pat. No. 6,020,218 to Shim et al show conventional encapsulation methods. U.S. Pat. No. 6,537,482 to Farnsworth teaches encapsulating the die with a resin. The references do not teach ways of preventing delamination at the die corner.